| Message ID | 20230518173403.1150549-3-catalin.marinas@arm.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | mm, dma, arm64: Reduce ARCH_KMALLOC_MINALIGN to 8 | expand |
On Thu, May 18, 2023 at 06:33:50PM +0100, Catalin Marinas wrote: > On architectures like arm64, ARCH_DMA_MINALIGN is larger than most cache > line size configurations deployed. However, the single kernel binary > requirement doesn't allow the smaller ARCH_DMA_MINALIGN. Permit an > architecture to opt in to dma_get_cache_alignment() returning > cache_line_size() which can be probed at run-time. > > Signed-off-by: Catalin Marinas <catalin.marinas@arm.com> > Cc: Christoph Hellwig <hch@lst.de> > Cc: Robin Murphy <robin.murphy@arm.com> > Cc: Will Deacon <will@kernel.org> > --- > include/linux/dma-mapping.h | 2 ++ > kernel/dma/Kconfig | 7 +++++++ > 2 files changed, 9 insertions(+) > > diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h > index 3288a1339271..b29124341317 100644 > --- a/include/linux/dma-mapping.h > +++ b/include/linux/dma-mapping.h > @@ -545,6 +545,8 @@ static inline int dma_set_min_align_mask(struct device *dev, > > static inline int dma_get_cache_alignment(void) > { > + if (IS_ENABLED(CONFIG_ARCH_HAS_DMA_CACHE_LINE_SIZE)) > + return cache_line_size(); > #ifdef ARCH_HAS_DMA_MINALIGN > return ARCH_DMA_MINALIGN; > #endif Maybe allowing architectures to simply override dma_get_cache_alignment would be a little cleaner rather than adding yet another abstraction? That might also be able to repace ARCH_DMA_MINALIGN in follow on cleanup.
On Sat, May 20, 2023 at 07:42:09AM +0200, Christoph Hellwig wrote: > yet another abstraction? That might also be able to repace > ARCH_DMA_MINALIGN in follow on cleanup. Looking at the rest of the series, this part is obviously not going to work..
On Sat, May 20, 2023 at 08:14:41AM +0200, Christoph Hellwig wrote: > On Sat, May 20, 2023 at 07:42:09AM +0200, Christoph Hellwig wrote: > > yet another abstraction? That might also be able to repace > > ARCH_DMA_MINALIGN in follow on cleanup. > > Looking at the rest of the series, this part is obviously not going to > work.. ARCH_DMA_MINALIGN needs to remain a constant (taking over from the original ARCH_KMALLOC_MINALIGN). But the dma_get_cache_alignment() can indeed be overridden by the arch code, it's a good idea.
diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h index 3288a1339271..b29124341317 100644 --- a/include/linux/dma-mapping.h +++ b/include/linux/dma-mapping.h @@ -545,6 +545,8 @@ static inline int dma_set_min_align_mask(struct device *dev, static inline int dma_get_cache_alignment(void) { + if (IS_ENABLED(CONFIG_ARCH_HAS_DMA_CACHE_LINE_SIZE)) + return cache_line_size(); #ifdef ARCH_HAS_DMA_MINALIGN return ARCH_DMA_MINALIGN; #endif diff --git a/kernel/dma/Kconfig b/kernel/dma/Kconfig index 6677d0e64d27..cc750062c412 100644 --- a/kernel/dma/Kconfig +++ b/kernel/dma/Kconfig @@ -76,6 +76,13 @@ config ARCH_HAS_DMA_PREP_COHERENT config ARCH_HAS_FORCE_DMA_UNENCRYPTED bool +config ARCH_HAS_DMA_CACHE_LINE_SIZE + bool + help + Select if the architecture has non-coherent DMA and + defines ARCH_DMA_MINALIGN larger than a run-time + cache_line_size(). + # # Select this option if the architecture assumes DMA devices are coherent # by default.
On architectures like arm64, ARCH_DMA_MINALIGN is larger than most cache line size configurations deployed. However, the single kernel binary requirement doesn't allow the smaller ARCH_DMA_MINALIGN. Permit an architecture to opt in to dma_get_cache_alignment() returning cache_line_size() which can be probed at run-time. Signed-off-by: Catalin Marinas <catalin.marinas@arm.com> Cc: Christoph Hellwig <hch@lst.de> Cc: Robin Murphy <robin.murphy@arm.com> Cc: Will Deacon <will@kernel.org> --- include/linux/dma-mapping.h | 2 ++ kernel/dma/Kconfig | 7 +++++++ 2 files changed, 9 insertions(+)